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Home , Anal columns, Gastric pits, Myenteric plexus, Peristalsis, Serous fluid, Submucosal plexus

Human Anatomy Unit 2

DIGESTIVE SYSTEM In Anatomy Today Abdominopelvic Quadrants Abdominopelvic Regions Body Cavities Body Cavities Serous Membranes

• A simple squamous and its underlying connective tissue – Produces a serous fluid – Lubricates, prevent frictional damage • Pericardial cavity – Visceral – Parietal pericardium • – Visceral pleura – Parietal pleura • Abdominal cavity – Visceral peritoneum – Parietal peritoneum Components of the Digestive System Functions

• Motility – ingestion – mastication – deglutition – • Secretion – exocrine – endocrine • • Absorption Terminology

• Ingestion • to take in food • Mastication • (mechanical breakdown of food) • Deglutition • • Digestion • chemical breakdown of food • Absorption • passage of nutrients from the gi tract lumen to the • Peristalsis • Waves of contraction to propel food • • formation and of solid waste

Mucosa

• Absorptive layer, large surface area • 3 major components – Mucosal epithelium • Columnar epithelium (, intestines) or stratified squamous • , Crypts of Leiberkuhn, Intestinal Crypts – folds in the mucosa of the small intestines, colon – source of new epithelial cells – digestive – • Loose CT of the mucosa, with capillaries that receive absorbed nutrients • lymphatic tissue: capillaries and lymphatic nodules involved in absorption of fat • Peyer’s Patches: aggregates of lymph nodes, significant protection against intestinal infections – Muscularis mucosa • a thin layer of smooth muscle that keeps the folds of the mucosa folded , Muscularis Externa, Serosa • Submucosa – tissue: dense irregular CT – • supply to the muscularis mucosa • Muscularis Externa – mostly a double layer of smooth muscle, propels and mixes digestive contents • circular layer: thick inner layer, muscle fibers describe a circle • longitudinal layer: thin outer layer, muscle fibers run along the length of the GI tract – : nerve supply to the muscularis externa • Serosa – loose CT + simple squamous epithelium – outer wall of the GI tract – Is the visceral peritoneum Movement Through the Digestive Tube Mesentaries

• Sheets of that connect the parietal and visceral peritoneum – Suspends organs in the space – Provides a route for blood vessels, , lymphatics • Lesser omentum • • Mesentery proper • Mesocolon • Transverse mesocolon • Sigmoidal mesocolon Oral Cavity The

• Body • Root • Papillae • Taste buds • Frenulum Salivary

• Release , lysozyme, digestive enzymes, – Salivary • Parotid – Pure serous – Parotid duct • Sublingual – Pure mucus – Sublingual ducts • numerous • Submandibular – Mixed serous/mucus – Submandibular ducts • numerous Teeth

• • Crown • Gingivae • Enamel • Dentine • Pulp cavity – Apical foramen • Periodontal ligaments • Cementum Types of Teeth

• Passageway for air, water, food • Divisions – Nasopharynx – Oropharynx – Laryngeal pharynx Swallowing

• Function – move food to the stomach • Lining epithelium – stratified squamous • Muscle layer – 1st third • – 2nd third • a mixture of skeletal and smooth muscle – 3rd third • smooth muscle Esophageal Gastric Juncture Gross Anatomy of the Stomach

• Lesser curvature • Greater curvature • Cardia – Cardiac orifice • Fundus • Body • – Pyloric sphincter • Rugae Layers of the Stomach Functions of the Stomach

• Functions – Food storage – Chemical digestion • Chief cells • Parietal cells – Mechanical digestion • Churning by 3 layers of smooth muscle – Kills bacteria – Moves food to SI – Hormonal regulation of digestion • G cells Histology of the Stomach

• Lining epithelium – simple columnar epithelium – Mucon neck cells • – microscopic folds, secrete gastric juice. • Gastric pits – openings from gastric glands to gastric lumen The

• ~ 3 meters long • Function – Digestion and absorption • • • • Support of the small intestine – Mesentary proper Intestinal Surface Area

• Plicae circularis – macroscopic permanent folds (permanent until death) – Circular pleats like conduit • Villi – fingerlike projections • Microvilli – submicroscopic folds on apical surface of columnar cells – “brush border” Histological Organization of the Small Intestine

Serosa versus Histology of the Small Intestine

• Intestinal villi • Microvilli • Goblet cells • Crypts of Lieberkühn Regions of the Colon

• – Right colic flexure • – Left colic flexure • • – Sigmoid flexure

• – Ileal papilla – Iliocecal valve – • The colon – Thin wall – Larger diameter – Haustra – Taeniae coli Appendix: an extension of lymphatic – Fatty appendices tissue near the ileocecal junction The

• Last 15 cm • • • • Histology of The Large Intestine

• Lacks villi • Abundant goblet cells • Intestinal crypts – Deeper – More goblet cells • Large lymphoid nodules • – Reduced longitudinal muscularis layer Accessory Glandular Digestive Organs

• Liver • Gall bladder • Pancreas Anatomy of the Liver

• Lobes – Left, right, caudate, quadrate • Ligaments – Falciform ligament • Liver to anterior body wall – Coronary ligament • Liver to diaphragm – Ligamentum teres hepatis (also called the round ligament) • Falciform ligament to umbilicus • Left, right hepatic ducts Liver Lobules

• Functional unit of the liver • Hepatic triad – Hepatic artery – Hepatic portal vein – duct • Bile canaliculi • Hepatocytes – Hepatic plates (cords) • Kupffer cells – macrophages • Central vein • Sinusoids The Gall Bladder

• Fundus • Body • Neck • Stores, concentrates bile • Ducts – Left, right hepatic ducts – Common hepatic duct – Cystic duct – Common bile duct • Hepatopancreatic sphincter – Ampulla of Vater – Sphincter of Oddi The Pancreas

• Head • Body • Tail • Pancreatic duct – Sphincter of Oddi • Accessory pancreatic duct – Duct of Santorini Histology of the Pancreas

• Pancreatic acini – Exocrine glands – • Islets of Langerhans – Endocrine glands – Alpha cells • glucagon – Beta cells • insulin Blood Flow